Right now, bonuses do nothing but say to you "I did this, hooray!" Which is kind of nice, make no mistake. But are there any plans to make them add something tangible? Maybe a reward for getting all of them on a dungeon? (Preferably not all at once, mind.)

At very least some bonus gold would be nice. There are some (like Cheeky or Ding Max) thare are pretty easy to do on a typical scenario and I don't think deserve rewarding, but on the other end of the spectrum stuff like Unstoppable and Purist are definitely worth reward.

Also, it'd be nice if Ying and Yang didn't count against "unstoppable", since they're often completely inaccessible.

If medals were tracked by dungeon the way classes are, they could serve as goal targets. So that a player can try to accumulate all medals for a specific dungeon, which would involve investigation of a variety of different strategies.

If that information is (optionally or not) collected online, players could look to see which medals and classes were particularly common/challenging for different dungeons, which provides feedback on accomplishment.

Great idea. And when u complete dungeon with all characters and earn all medals in that dungeon u get something.That something can be anything like extra item, improved item, some kingdom improvement, ability to take more bonuses when u prepare for dungeon, ability to take more gold in dungeon and so on.And then u can make extra vicious dungeons where all those bonuses would get handy:)

There are already quests for defeating dungeons with a variety of specific classes or badges already exist. Bulking them out to include every combination would mostly just make them grindy. (There are several Monk purist quests, Bloodmage faithless quests, and a currently notorious Wizard warmonger quest).

Defeating some dungeons with every class and accumulating every medal would be so hard that having useful rewards from it would be counterproductive. I really think bragging rights would be enough. Trying to get Purist or Warmonger in Namtar's lair is harsh enough that it doesn't need a harder tier after it; that time would be better off spent on another dungeon in a more accessible range.